Fuel burning air heater



Jan. 8, 1952 A. R. COLLINS ETAL f 2,581,942

FUEL BURNING AIR HEATER Filed July 17, 1,946l y 11 Sheets-Sheet l Jan. 8, 1952 A. R. COLLINS Erm. 2,581,942

FUEL BURNING AIR HEATER Filed July 17, `194e 11 sheets-sheet 2 M, mw

@Zbl/mega Jan. 8, 1952 A. R. COLLINS Erm. 2,581,942

FUEL BURNING AIR HEATER` v Filed July 17, 1946 11 sheets-sheet s i 2,5&1,942

11 sheets-sheet 4 A. R. COLLINS EI'AL FUEL BURNING AIR HEATER Jan. 8, 1952 Filed July 17, 194e Jan. 8, 1952 A. R. COLL-INS ETAL FUEL BURNING AIR HEATER 11 Sheets-Sheet 5 Filed July 17, 1946 Jan. 8, 1952 A. R. COLLINS ETAL FUEL BURNING AIR HEATER 11 Sheets-Sheet 6 Filed July' 17, 1946 Jan. 8, 1.952

Filed July 17, 1946 A. R. COLLINS ErAL FUEL BURNING AIR HEATER l1 Sheets-Sheet 7 Jan. 8,1952 A. RCQLUNS mi 2,581,942

FUEL BURNING AIR HEATER.

Filed July 17, 194e i1 sheets-she@ e Jan. 8, 1952 A. R. COLLINS r-:rAL 2,581,942

FUEL BURNING A HEATER Filed July 1:7, 1946 11 sheets-sheet e 16 35g n f7 Jan. 8, 1952 A. COLLINS ETAL 2,581,942

I V FUEL BURNINGI AIR HEATER Filed July 17, 194s i 11 sheets-sheet 1o,

lr//lllll//ll'llll/r lllllllllllllllll A. R. COLLINS x-:TAL 2,581,942 FUEL BURNING AIR HEATER v 11 sheets-sheet 11 Jan. 8, 1952 Filed July 17, 1945 Patented `an. 8, 1952 Randall,

Indianapolis,

Ind., assignorsto Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia Application July 17, 1946, Serial No. 684,350

(c1. V12e-110) 9 Claims.

The present invention relates to heaters and primarily to space heaters of the gas-fired type, although certain aspects of the invention are applicable to heaters using other fuels.

Domestic heating equipment of the most favored hot air type comprises a central furnace which is connected to remotely located outlets and inlets by means of rather extensive ductwork. Usually air is forced through the furnace and through the ductwork by an electrically driven blower. A system of this type is conventionally controlled so as to give on and off cycles of sufficient duration to supply just enough heat to balance the load condition. A thermostat sensitive to the temperature at one point in the space to be heated usually acts to turn the system on or ofi. I

A system of this type is expensive largely because furnaces are not standardized and because of the complexity of the ductwork which must be e built on the job. Since the furnaces are not standardized, control systems cannot be built in large production for a particular furnace but must be built so as to be adaptable to many types of furnaces. In addition, such furnaces are diicult to service particularly with regard to removing and servicing the burner and in replacing the burner if necessary.

The present invention makes the use of ksuch duct systems unnecessary and is thereforelwell adapted for installation in houses already built and in which no duct system was incorporated at the time of building.

In all houses, and in smaller houses particularly, the portion of the cost of the building incorporated in the chimney is relatively large. Such chimneys are necessary with central heating plants, but are not needed with the heater of the present invention. It is apparent, therefore, that the present heating systemsaves a substantial element of cost normally found in most houses.

A further object of the present invention is to provide a heater and heating system in which the air for combustion is all taken from outside the building, passes through the burner, vand is then exhausted outside the space to be heated `With the result that no gas contamination within the space to be heated is possible and further that an explosive atm-osphere within the space to be heated, such as may occur in a garage, filling station or the like, will not be ignited, since there is no communication between the air space within the space to be heated and the fire.

l Still another object is to provide an improved heater of comparatively high heat output which is gas fired, which has forced air circulation, and

which is compact. Still another object is to provide a heater of this type which may be installed in a variety of `ways by the simple substitution of interchangeable,

standardized parts. f

Yet another object is to provide a small, .rela-A tively inexpensive heater which operates as an in. dependent unit including the control system and which is therefore readily adapted for use either singly or in groups of two in small, low-cost houses where the cost of the heatingsystem preferably should be kept low or, which is equally adapted for use in larger groups in larger and more expensive dwellings under which condition the full advantage of uniform air vdistribution and low heat output per unit and therefore more quiet operation is more fully realized. In either event, a heater constructed according to the present invention should provide an improved heating system in a dwellingof almost any sizeor type at the same or lower cost than hot-air heating equipment now available. Y

An additional advantage is to provide a heater I for accomplishing the above which is well adapted to mass production methods and which may be installed with minimum effort. Y

' Other objects and advantages will become apparent from the following description of a prei ferred embodiment of our invention which is i-llustrated in the accompanying drawings.

' In the drawings in which similar characters fof reference refer to similar parts throughout'the several Views:

Fig. l may be considered as a front view of ra heater incorporating the present invention shown with the front of the case removed so as better to disclose the interior mechanism;

Fig. 2 is a top View of the heater illustrated in Fig. 1.` Inthis view the top portion of thecase has been removed so as better to disclose the arrangement in the interior thereof Fig. i3 may be considered as a viewlookingla't the right end of Fig. 1 showing the general loca;- tion of the heater mechanism'within'the case;

y Fig. 4 is a left end view of the heater illustrated in Fig. 1. In this view a portion f the mechanism has been broken away so as to show structure'inl teriorly thereof; l

Fig. 5 is similar to Fig. 1, but shows the back side of the mechanism;

Fig. 6 is a vertical longitudinal sectional view vof the left-hand portion of Fig. 1 illustrating .primarily the burner, heat exchanger, and asso; Vciated mechanism;

Fig. 7 is a vertical transverse sectional view taken along the line 1 1 of Fig. 6;

Fig. 8 is a bottom view of a portion of the burner strip and associated mechanism;

Fig. 9 is a top view of a fuel control regulator forming a portion of the present invention shown with portions. of the case wall broken away lso as better to disclose the interior structure;

Fig. 10 is a medial sectional View of the regulator which may be considered as taken substantially along the line lil-I0 of Fig. 9;

Fig. ll is a side view of a heat output regulator or motor controller which modulates the heater Vaccording to demand conditions;

Fig. 12 is a vertical sectional View which may be considered as taken in the direction of the arrows substantially along theV line tlf-t2 of Fig. 1l;

Fig. 13 is a longitudinal sectional viewV in a vertical plane of an overheat control forming a portion ofthe present invention;

Fig. 14 is a transverse sectional View which may be considered` as taken in the direction of the arrows substantially along the line i4--l4 of Fig. 13;

Fig. 15 is a sectional view similar to Fig. 14, but taken in the direction of the arrows along the line |5-I5 of Fig. 13;

Fig.`16 is a top View of a flame detector forming a portion of the present invention;

Fig. 1'7 is a front view of the flame detector illustrated in Fig. 16;

Fig. 18 is a partial sectional view showing a damper foradjusting the combustion air rate;

Fig. 19'is a front-view of the heater cabinet;

Fig. 20 is a sectional view through the cabinet taken in a Vertical plane substantially along the line 2-20 of Fig. 19.

Fig. 21 is a vertical sectional view similar to Fig. 20, but showing additional cabinet elements which may be used if desired; and

Fig. `22 is an electrical circuit diagram suitable for use with the heater of Vthe present invention.

GENERAL THEORY AND MODE oF OPERATION Among the essential characteristics of Vthe heater of the present Yinvention are that it be extremely compact and self-contained. and need connection only to a source of fuel gas and Aelectric power and have connections to air intake and exhaust pipes, both of which can pass into ahollow wall and rise vertically therein to the roof. A suitable arrangement for bringing in air for combustion and for removing the exhaust gases is disclosed and described in the now abandoned application of Theodore Y. Korsgren and Frank A. Ryder, Serial No. 596,130, which is assigned to the assignee of this application.

The heater is intended to be used primarily without ductwork, although there is no objection to, and infact the invention contemplates the use of, some ductwork under some conditions. However, since the heating load is distributed among several advantageously located units, the ductwork for eicient distribution of the heated air, even at most, is, of course, of comparatively minor extent.

The individual heaters draw in a portion of the air from the space to be heated. and this air is passed through a heat exchanger and is then reintroduced into the space, thereby setting up a circulation of air toward andV away from the heater. This circulation is brought about by an electrically driven blower, the speed `of which is automatically modulated according :to lthe de- 4 mand for heat. In mild weather the blower will operate at low speed while in severe Weather the speed will be considerably higher. By the use of several heaters properly located so that the demand upon any particular heater is well below its rating, the blowers at no time, or, at least, at no times other than possibly under conditions of severe cold' will be operated at outputs even approaching their capacity. With such a system the heaters Will have an extremely low noise level. As will be seen from the above, the primary control over the heater is exercised by controlling the blower motor speed. This blower motor drives both the Ventilating air blower and a f combustion air blower, so that the combustion air rate and Ventilating air rate will track. Control means is incorporated in the heater so that the rate of combustion air flow determines the rate of fuel supply. Thus, the mixture ratio is kept constant under all operating conditions and the heat output tracks with the Ventilating. air rate. The temperature of the Ventilating air therefore remains substantially constant under all conditions. The ultimate result is that air for heating is circulated at approximately the same temperature at all times, but under severe conditions more of this hot air is circulated than when the weather is mild. Since the temperature is constant it can be set at such level that the warm air feels neither too hot nor too cool to the occupants of the room. inasmuch as the blower is operating substantially constantly regardless of the heat demand, it will be seen that the circulation of the air Within the space is Well maintained, thereby preventing stratification of the type which usually take place with ordinary warm-air heating systems whenever the room thermostat is satisfied and. the blower is turned off.

Because a heating system using heaters of the type forming the subject of the present invention is built around units which can be fabricated by mass production methods and in which very little work upon the premises is necessary to complete a particular installation, it is apparent that the total cost of theultimate heating installation is divided in such manner that almost all of the work is done at a factory where it can be performed more efficiently than is possible at the premises. Further, since the heat load in a particular installation will be divided among, as a rule, two or more heatingV units, it follows that a higher and more elicient rate of production can be achieved upon a single type unit than is possible upon larger furnaces whereV only one is used in each dwelling. This eiect uponthe relative costs of the two types of systems is still further exaggerated by the fact that so long as a house is heated by a single furnace it is necessary to build. furnaces in different sizes for different sized.- houses, whereas when a single basic unit is used in groups of two, three, four, five or more, much higher production and therefore greater production eiciency can be achieved in the standardized model.

By kthe use of. individual heaters, each of which is individually controlled, it is feasible without complication to maintain different zones throughout the dwelling at different temperatures. Thus, one or more heaters may be installed for handling the heat load of the bedrooms of a house andv these "rooms can therefore be maintained at a lower temperature than the living room, for instance, which may have its own heater. Workshops and garages .can be maintained at still ;k lower temperatures, if desired. For instance, they may be kept just above the freezing point most of the time and then simply by moving up the setting of the thermostat, these rooms can quickly be brought to any desired temperature.

Although heaters of the present type can be constructed to have any desired output, the particular heater shown operates up to approximately 20,000 to 25,000 B. t. u. per hour. Thus, two of these heaters have Sucient capacity to heat the average small house in the northern portion of the United States. In more elaborate installations where more heaters are used so as to obtain the best distribution of heated air, each heater will normally operate at well below the 20,000 B. t. u. heat output level even in extremely cold weather and therefore rooms, or, in fact, the entire dwelling can quickly be brought from a low temperature to a suitable level when desired. In other words, it is feasible to permit the temperature within the dwelling to drop to just above the freezing pointfduring even comparatively short periods when the house is not occupied and then when the occupants return, the thermostats can be moved'to the desired setting, whereupon the heaters will operate at their maximum heat output so as to bring the temperature within the space to a satisfactory level in just a few minutes.

Since under normal conditions the heaters will continuously modulate their heat output between high, low and intermediate points, they are not often called upon to start and stop and therefore the noise inherently incident to the starting and stopping of any typeheating system is largely avoided. This is a particularly advantageous arrangement when heaters are located within the living space rather than being remotely located as is a conventional furnace, it being obvious that whenever heaters are installed either directly in a living room, for example, or recessed in a living room wall, a lower level of noise should be maintained than can be tolerated when a heater is remotely located.

Y l GENERAL ORGAN'IZATION `OF THE HEATER ELEMENTS -Referring to the drawings, the heater there shown includes a chassis I0 enclosed within a cabinet or case I2. In general, the cabinet is rectangular in all planes excepting for rounded corners and edges and will be described in greater detail subsequently. The chassis I0 "comprises a frame I4 which encloses and supports the major operating elements. This frame is made up of rectangular sheet metal plates, with-cut out portions and flanged edges, welded or otherwise suitably secured together at their corners and edges to form a skeleton box-like structure. One end of this frame, the left-hand end in Fig. l, does not have an inturned flange but is closed by a plate I6 which serves as a stiffener and fire wall or partition or baffle to separate the heat exchanger and combustion chamber from the accessory compartment. For convenience/in reference,lthe portion of theheater mechanism to the right of this wall, as seen in Fig. 1, will be referred to as the accessory compartment.'

"In general, the accessory compartment contains a variable speed electric motor lrsecured to a diagonally extending subframe 20 which in turn is secured in the main frame I4 by means of soft rubber shock mounts 22 for isolating motor, blower wheel and belt vibration.

- 'One end of the motor shaft, theright-hand end as seen in Fig. 3, is connected directly to a centrifugal-type blower wheel24 located within a-.scroll case 26. The scroll case is secured directly to the frame I4 and is connected by ductwork 28 to a combustion air plenum chamber 30, as best s-een in Fig. 6. v

y As will be` described in greater detail presently, air from the duct 28 flows into the plenum chamber 30 and from there a portion of it mixes with the fuel gas and passes to the burner, while an additional portion supplies secondary air for combustion, the burning taking place within a combustion chamber 32. From the combustion chamber the hot products of combustion ow downwardly, outwardly, upwardly and then inwardly, as indicated by the arrows in Fig. 4until they reach the top of the heat exchanger indicated generally by the numeral 34. At this point they make connection with an exhaust fitting 36 from which the products of combustion are con-v 44 leading toward the right of Fig. 1 to a positionin approximate Vertical alignment with the inlet opening of the blower 24. An elbow and adapter conducts the air downwardlyfrom this point to the blower inlet. The entire combustion air, burner, and exhaust system, therefore, is sealed and communicates at both ends with the atmosphere outside of the building. y

At its left-hand end, as seen in Fig. 3, the shaft of the motor I8 is equipped with a pulley 46 which drives a Ventilating air blower pulley 48 by a V-belt 50. shaft 54 journaled at each end in bearings 55 supported by the downwardly inclined subframe 20 which also supports the motor I8. A Ventilating air blower wheel 52 is mounted upon the shaft 54 and is, therefore, held in fixed alignment relative to the motor I8 but is shock mounted along with the motor with respect to the heater main frame. v

The Ventilating air centrifugal blower wheel 52 is disposed within a scroll case 58 located adjacent the lower right-hand portion of Fig. 1, this scroll case on its outlet side being connected to a sheet metal duct 60 leading to the Ventilating air inlet of the heat exchanger 34. On its inlet side the Ventilating air scroll case 58 simply opens to the space within the cabinet I2l and since this cabinet communicates with the space to be heated through louvers to be described in greater detail presently, louvers, into the scroll case 58, and is passed by the Ventilating air blower to the heat exchanger 34. After being heated within the heat exchanger the warm air passes from the outlet end 62 thereof into the space within the cabinet I2 on the opposite side of the fire wall or baile I6. It therefore finds its way out into the space to be heated through a second set of louvers.

A group of accessories is located within the frame I4 in the upper right-hand corner, as seen in Fig. 1, and comprises a fuel pressure regulator valve B4,l shown in greater detail in Figs. 9 and 10, and a box 65 which contains a pair of relays and a step-down control transformer 86 which has a primary operating at the line voltage of approximately volts and a secondary whichl The pulley 48 is secured to a cross air is drawn through these very emeient for this purpose andthe capacitor.

80 for-'shading'theappropriate motor` winding is located ina'vertical position just insidethe hre wall adjacent onev of the vvertical sides of the frame I4 in a position near Jthe top thereof; This capacitor-may moet easilybefseen in FigQZ.

A time-delay lock-open type switch .tor be deY scribed subsequently is located within a box 82V positioned towardl'the right-hand end of-the frame, as seen in Fig. 1. It is justbehind the scroll case 54 for the Ventilating air blowerand may bestbe seen in Fig. l. i Y

The fuel gas is 'brought-into the heaterthrough a pipe 84 provided Aat its end withV a anged adapter 86 whichis secured toa matching flange 38 mounted upon the heater. The flange 88 is secured to a fuel tube 90 which communicates with the fuel' pressure regulator at the fitting 92. The fuel gas afterre'gulation leaves the re'- gulator- 64 by wayrof a fitting 94 which leads to a tube 96 which passes'downwardly, longitudinally, and then upwardly-alt an angle to a fuel nozzle `98 located at the open end of an air aspiratilng 1'."

fitting inthe plenumchamber 30. This as'- pir-ating fitting communicates at its downstream end with an elbow IUZYleading to a gas burner A| 04 having a manifold and a multiplicity o'f down-V wardly extending burningvopenings m6 located within the combustion space. Secondary air for combustion passes directly from the plenum chamber 60 into the combustion chamber byway of a comparatively large-opening |-08Yin the vend Wall of the heat exchanger.

Burner and heat exchanger The heat exchanger indicated generally by the numeral 3d is constructedof heat and corrosion `resistant sheet metaL'such as high alloy stainless steel, fo'r instance, the cut and formed'pieces of metal being'welded into a` unitary substantially air-tight structure. More specificallyy the heat exchangerrnay be pictured as an oval, horizontally-disposed sheet metal tube with a longi 4inner surface cf the. Vouter sheet llt.. The cx:

haust elbow 3.5 passes through a. longitudinally `extending strip H8, the edges of Vwhich are crimped, as at, mil, to the upper ends of the outer sheet I4. The inner or lower.v endsofthe elbow 361s welded to, the Surface of the inner tube lill and communicates With the space inside this inner tube through a Suitable opening.

in orderiio. obtain. more neat-exsziieuscsurface.

(iii

i nozzle projects.

and a. better distribution .of the; hot;V products .off

combustion against the. surface of the. sheet Uli,v a hollow horeshoe--shapedY baffle 22 formed.prei?.-V erably of a continuoussheet. of stainless steelor thev equivalent 'is in effect draped around the. burner manifold ||2 in a position between the burner manifold and the sheet HS, and extends. downwardly. almost to the lower end of the space. within the sheet. Hi?. The hollow baiiie |22. may; be considered as an oval tube, approximately one half of which has been bent inwardly to form. a re-.entrant surface within the major portion. The spacing. within the hollow. baiiie is such that air hows more. freely. therethrough in. a longitu-V dinal direction near. theV lower, portion thereof than adjacent the. .top portion.

The space within the heat exchanger which connes the products. of combustion is closed by end plates |24. which extend across the areas circumscribed by the ends of the sheet |10, with.

the exception of the ends of the horeshoe-Shaped tube formed within the, hollow baffle. 22, these end plates being welded to the sheets i. it, and [22.. Thus, whenever there isa .pressure differential between the two ends of the heat exchanger, il? will now longitudinally through the horeshoeshaped passage within the hollow. hafe |22; and' through the annular space between the. Shoe-LS. Hai and H0.

The burner manifold t2 extends longitudinally through the upper. portion of the inner; chamber of the heat exchanger from end to. end thereof. At the downstream, or left-hand, Vend as seen in Fig. 1, the manifold is closed, While. at its opposite or inlet end it is equipped with the elbow H12 which extends downwardly at an. angle of approximately sixty degrees o r so, to its inlet where it. is connected to` the gas. aspirator.. |98 previously mentioned. The, eas nozzle. 9.8., also previously mentioned, is positioned in axial alignment with the inlet opening of the aspirator and alignment is maintained by a spider |26y secured to the end of the aspirator, the spider having a central opening |21 through which the Thus, fuel gas flowing through the fuel pipe 96 and nozzle 3 8 will reduce the pressure adjacent the inlet opening of the aspirator so as to draw primary air inwardly, thereby forming a rich gas and air mixture. This mixture passes into the. mprnfQld and iOWS. *Sheltefrom in a downward direction through a multiQA plicity of burner openings H36l formed in a longitudinally extending strip in the lower portion of the manifold.

The plenum Chamber indicated generally by the numeral 30 is formed as a sheet metal cup with the bottom secured directly within an openV ing in the upstream end plate |24 of the heatk exchanger so as to provide an outwardly. extending sleeve or cup |28 which projects a short distance into the accessory compartment lil. All but they lowermost portion of this sleeve conforms to the general shape of the upper portion of the inner surface of the hollow bailleV |22 (Fig.4 Ll). 1n other words, it conforms to the shape ofthe upper portion 0f the Combustion chamber et its inlet end. At its lower end this opening terminates on a line approximately halfway be-- tween the top and bottom gf the heat exchanger.

The space inside the sleeve |28 communicates directly with the upper portion of the inner heat exchanger chamber by way of an opening |31] in the end of the cup through which the burner manifold extends. This upper portion of the heat exchanger, that is. the portion, within which the burner manifold is located, is indicated by the numeral |32 and is separated from the space below the burner by a pair of downwardly inclined side plates |34 which extend alongside the burner manifold at its lower edge throughout its length, these plates being slightly separated from the edge of the manifold to form a pair of slots |36. The plates and burner manifold are secured in assembled relationship by generally wedge-shape brackets |38 which are welded to the plates |34 and to the burner tube.

The manifold is placed in the heat exchanger and combustion chamber by sliding it in endwise so that the plates |34 fit into slots |40 formed between a pair of sheet metal ribs |42 which are located in parallel relationship and form the slot |40 therebetween. The strips I 42 are welded to the inner surface of the heatvexchanger wall on both sides. This construction serves to divide the interior of the heat exchanger into the upper chamber |32 previously mentioned and the lower combustion chamber, these two spaces communicating through the slots |36 alongside the fuel openings in the lower portion of the burner manifold. Thus, air which finds its way from the plenum chamber through the opening |30 is forced downwardly through the slots |36 and serves as secondary air to complete combustion of the rich fuel and air mixture passing through the burner openings |06.

At the plenum chamber end, the plates |34 are connected to a downwardly extending flange |44 which lies in face-to-face relationship with the closed end of the cup |28 when the burner tube is in assembled relationship to the heat exchanger. This liange |44 is sealed to the closed end of the cup |28 by means of screws |46 which extend through the fiange |44 and are threaded into the closed end |28. The iiange |44 also has an offset portion I 48 which is welded to a bushing |50 into which the spark plug 16 is threaded so as to position the spark plug terminals adjacent the gas outlet openings.

In order to make the heat exchanger and combustion chamber portion of the apparatus easily removable for servicing, the gas nozzle 98 is threaded to an adapter |52 welded or otherwise suitably secured to the wall of the plenum chamber 30. The inlet end of the nozzle is connect-J ed to the gas pipe 36 by a union-type fitting |54. In order to remove the heat exchanger and burner from the remaining portion of the heater, it is necessary merely to carry out the following steps. First either front grill 446 or back plate444 (Fig. 20) is removed to permit access to the compartments on either side of the partition I6. The exhaust elbow 36 is disconnected from the exhaust pipe 38 at a flange indicated by the numeral |56. The gas pipe 96 is disconnected at the union |54. The combustion air inlet pipe 28 and an elbow |58 at the upper end thereof are disconnected from a pipe stub |60 which leads into the plenum chamber 30, the elbow |58 and stub |60 being joined by a removable clamping ring |62 of any suitable type. After the above-mentioned connections have lbeen broken, the heat exchanger can be slid in an endwise direction out of the opening in the fire wall I6, the lire wall and heat exchanger being connected simply by a friction fit. After the heat ,closes the outward end of the plenum chamber is removed, and the nozzle. 98 is unscrewed from its bushing |52.

Also, the screws |46 which se.

cure the ange |44 against the lwall l|28 are taken out` so that the burner'tube can be slid out of the combustion chamber in an endwise manner. After the burner tube has been at least partially removed, the spark plug 16 can be conveniently taken out of the bushing |50. The parts may be reassembled by reversing the process.

The combustion air supply system Combustion air enters the heater from outside the vbuilding through the pipe or duct 40 previously mentioned. From this duct the air flows through the adapter 42 and elbow 44 and thence at right angles through the re wall I6 into the accessory compartment. This horizontally extending portion of the duct, indicated by the numeral |66, is comparatively thin from top to bottom and wide from side to side so as to crowd the accessory compartment as little as possible. At the point where the end of this duct |66 comes into vertical alignment with the motor I8, it connects with a double elbow which changes the directionof the duct system toward the rear wall of the cabinet and thence downwardly to an adapter I 68 which covers the inlet opening of the combustion air blower case 26. y

The outlet end of the blower is best ,seen in Fig. 5 where it is indicated by the numeral |10. This outlet opening connects to a sheet metal formed duct which extends downwardly and slightly toward the fire wall for a short distance where it is connected to a venturi |12, the outlet of which leads to a diverging pressure recovery section I 14 which curves downwardly, toward the iire wall, and thence upwardly alongside the nre wall to the elbow fitting |58 previously referred to. From the outlet of this elbow the air passes through the clamping ring |62 and stub |60 into the combustion air plenum chamber. Y

Inasmuch as different installations of the heater will impose different amounts o f pressure drop upon the combustion air system, depending upon the length and restrictive effect of the inlet and exhaust pipes, a small damper |16, best seen in Fig. 18, is located in the elbow |58. This damper is `of the buttery type' and is mounted upon a shaft |18 which extends through the side wall of the elbow and is provided with an adiustment knob yat the end thereof. The damper shaft has a comparatively tight iit so that although it vcan be adiusted manually to give the combustion air side of the heater .the pressure drop characteristics desired, there The ventilatng air circulating system The Ventilating air scroll case 58 previously referred to receives air directly from the accessory compartment through the opening |82 which is faced away from the grilled opening of the cabinet, since by. so doing less blower noise gets into the space to be heated. From-the opening |82 tholttomloy cross-.strutsf-l8secured'- theretoso `as to form a ssuiiiciently fstiff structure.

of thisfframe .are .connected :to the'insidefends .of .rubbers` shook :mounts 122i previously mentioned, fthe-.opposite .ends of which A.are secured in :the .f-framail As shown,.the frame-.Mhas-a lstiifeningamemloer-/LSU on each sidewhich ,paral-lelethe i .sside rails .|184 :and .186. .The shock :mounts 22 @comprise .fa ,shori', length of .-fsoft rubber, :with Vits :ends vulcanized to rmetailic .buttons which V.are adaptedifor attachment-to the framezimembers. .Shock .mounts offthis Vtype are IvWel1..1frnown#and Aneed Inoefurther description here. Prefer-ably, to providesadjustmentffornthefshockrmounts, the ,fastening element `on Ythe .ou-ter -.ends ...passes .through .slots |192j in .the frame. so :that the: outer rends can :he loosened-fand moved about so las ;.properly .to .locate theJtWo blower wheels relative ...to .their scroll ucases; -Y

l:The .motor 4Bris .provided with -bell-s 'L94 at .its .ends .which Vare secured .in .soft rubber' rings .encompassed my .bands 19.8 -carried =by the f-sub .frameamembers yI 84'and |186. ,These rubberv rings, ttherefore; absorb themajor .por-tion. of the :linear .vibration of themotortand 4`practically allof the ,axial vtorsional `vibration. The -ventila-ting `air blower shaft-.544s.providedfatts endswith Vbear- .ngs w56 which.similarlyfare-parried in'soft'rubber .rings 1,98 .secured .in openings in the subframe 484. This eonstruction 'results in fmost -of Vthe `.motor vibration `-andithe .wheel Vvibration being :isolated/.from vthefsubframe ifand what vibrartion-.doesnot-reachthesubframes isolated from :themain.framebysshockimounts 22. The result `is -that -.the :motor and blower wheels Aoperate rextremely.quietly.

The fuelpressure regulator and system associated therewith The venturi 2112 in theY combustion air line iis provided iwith a pressure vtap f2fill (Fig. l'5) which Vis .fconnected by fa tube 202 to'a low prescsure vfitting 204 of 'the fuel controller' F, 1best .shown Figs. 9. and 1'0. A second 'pressure tap 206 is located `'upstream of J:the venturi and isicormectedfby. alinerZB to a. high pressure .tap 'Zmfof the v`controller '64. The 1control valve vfli also -has a thirdtapf2'12 which may be -con- `siderecl as an atmospheric pressure tap. Actually, `it yconnected 'by way of 4a 'line 2M with fa 'fitting 2i@ `'in the sidewall of the plenum 'chamber lso fthat `this tap 'approximately sensitive ftd-the' pressure at the `lburner.

Referring now to Figs. 9 and 10 whichillustrate thecontrol valve in detail, t..wi11 .be seen that the device comprises a casting 2|8 provided at one side-with Va chamber `22? connected 4.to .an inletl .fuel fitting 92. In order to remove solid -or gummy matter from Athe fuel, the fuel passes from the yfitting 92 `into -a line Vmesh screenlterelement 224 located Within Ithe chamrber 220 and thenceY outwardly through the :The "ends opening-sin the 'screen fintoftne :chamber free 'proper'. From here -thefruel glas passe's't' a port-226 into a vvalve chainber'l228. TSO n insure the fuel being'ftrned io'ff completely whenever fheai'er pper'at-ion is fshut down, 'the por-t i2 2e jis `proxfitled with -a Yxftilve seat 23e fand with'la poppetfvalve v"2?2 loca-ted in operative frelatioI-iship`ther'evvi'th.` This Ipuppet Valve has fa soft-"seat andi-islconnected lto anf'aimatur fE-@e Aofa.solenoid 23's. Normally, the popp'et valve 232 is urged intoplosedi'postin by a coilsprin'g "238 -so yas 'to close o'l communication 1between thefchamber 221i and lthe valve 'chamberg'a Tne'two 'e1ectiica11e'ads its of the soienoidare .l broughtout'and secured to insulating terminal posts 242 to `which lelectrical vcoiin'ect-i'oris htemeer; from the outside, these :two terminal posts passing through the casting 2i8 wheiewit '-forms 'the lower iside. wall 'of "the chainbe'rZZ'. Whenever-the solenoid 2st is energized eie'ctjrically,'fthe arniaturef'sl will beurgedfdownwardly so as to move the poppet 232 away from 'the 4valve seat Vv230, therbypermitting fuel :gasto "low'fromther'inle't rtti'ng 92 tothe valve chain- 25 ber 228.

V''llie valve chamber T2218 rvcomprises Va vdrilled passagefthrough'the casting which intersects'the -port 226. One end of 'tlis'paSSa'ge "228 is 'pr'o 'vided with 'a VValve "Seat :2134 Yvvh'cll cooperates with a cone type'valve'G-'nounteduponia valve "stem"2'fif8. The Valve js'eat24"4 is "foririedin a bushing 2553 i pressed intothe "passage l22 8, Just 'beyond the bushing 2'5la'pairof spaced'lexible 'diaphragme '2'52 and 251i 'are 'clamped at 'their edges around an annular ring 255 bymeans yof a sheet-'metal cover plate 251 and'asimilar 'plate '259 having an openinginithe center thereof,`the plate '259 being secured by Imeans o f screws, 'not shown, to the face of the casting 218 substantially concentrically with the vvalve stein 243. `In order to insure a tight seal, the surface of 'the-casting Vat the point of securem'ent to Athe plate 25S "is preferably counterbored as atV 258 and a soft rubbergasket is interposed between the two surfaces. The annular ring 258 is formed 'integrally lwith a centrally Adisposed parti-tion 262 which divides the Iregion between the diaphragms into separate spaces, the Space Vadjacent the diaphragm 252 being indicated by Vthe numeral 264 while the outermost Yspace adjacent the diaphragm 254 `is denoted by the numeral 266.

The valve stem on the inlet side is secured :to the center of a thin iiat spiral spring 2lu'which is formed by cuttinga pair of spiral slotsthrough a thin spring metal disk.V 'The edge of the disk is secured in the bottom of a counterbored opening -212 by `a ring '214 held in place by a` cover plate 216. vThe spring applies slight pressure to the end of the valve stern 268 `so as to urge the valve 236 toward closed position. This pressure, however, is very slight and the purpose of the spring primarily is to center' the valve `s't'em and vto 'cause it to follow the diaphragrns rather than to apply any considerable pressure thereto.

The opposite end `portion of the valve 'stein passes through a guide 218 'securedto the upper end of the bushing '250 and its end is in'engagementwith a button 280 vsecured to the rlower surface of the diaphragm 252 so that downward movement vof the diaphragm Willmove the valve 24o toward open positionwhile the soft 'spring 210 causes the valve to follow the diaphragm when the diaphragm moves in the opposite direc- 75 tion.

Vthe diaphragms at their centers are provided with backing plates 286, vthe centers of which yare cut to form tabs which are rolled into flattened. ovalshape and are drilled in alignment with the pin 284. These tabs, indicated by the numeraly 288, act to support the diaphragme from the pin '284 regardless of the position of the device. v

As best shown in Fig. 10, the highfpressure tap 2 I El communicates through the cover .251 with the space 290 between the cover and the diaphragm 254. The space 266 on the opposite side of this diaphragm communicates by way of a passage 292 formed in the edge portion of the annular ring 256 with the fitting 284, this tting being connected, as has previously been mentioned, with the low pressure point of the combustion air venturi |12. The space 264 between the partition 262 and the other diaphragm 252 vis connected by way of the tting '2I2 tothe plenum chamber at the burner. The remaining space, indicated by the numeral 294, on the opposite side of diaphragm 252 is of course sensitive to the pressure of the fuel on the outlet side of the valve 246. This chamber is connected by way of a passage 296 to a ntting 298 connected to the gas pipe 96 leading to the burner.

The fuel pressure regulator operates in the following manner. Whenever the electrical circuit to the terminals 242 is energized, the poppet valve 232 will be opened by the solenoid 234, thereby permitting gas to flow to the modulating valve 246. If, now, it is assumed that the combustion air blower is operating and that the pressure in chamber 266 is lower than it is in chamber 298 since combustion air flowing through the ductwork will cause a lower pressure at the venturi |12 than at the high pressure tap '206, it will be seen that the pressure differential will tend to cause the diaphragm 254 to move toward the right, as seen in Fig. l0. As soon as it moves slightly, the valve 246 will be opened and gas will flow into the chamber l294 and thence to the burner by way of the passage 296. Inasmuch fas the pressure in the chamber 264 is at the level of the burner, or, in other words, substan tially at atmospheric, the pressure of the gas will build up until the difference in pressure between the gas and the combustion air at the burner, this pressure diil'erential tending tomove the diaphragm 252 toward the left, balances the forces acting on'the diaphragm 254. The burner,

therefore, continues to receive fuel at the rate established by this balance. If, now, `the combustion air blower is increased in speed so as to increase the differential tending to move the diaphragm 254 toward the right so as to open' the valve, it will be seen that immediately the-gas pressure in the space 294 will rise until a new balance is found, after which the burner con-V tinues to operate at a higher output since it is receiving both more combustion air and more fuel. Thus, by the expedient of simply controlling the speedof rotation of the rcombustion air blower,

`the heat output can be xediat any desired level -within the range of operation of the heater and under all such conditions the fuel air ratio will remain substantially constant, thereby insuring efcient combustion. 4

In Fig. 9, it may be noticed that the three pressure taps 284, 2H) and '2I2 are radially separated so as to facilitate making connections to these taps. In Fig. 10, one of these taps Zit has arbitrarily been moved into radial alignment with the tap 204 so as to be in the plane of the section for the purpose of illustration, since it is believed that by so doing the construction and mode of operation will be made more clear. The pressure tap 2I2, however, has been permitted to remain in its actual location since the passages in the annular ring 256 for making connection between this tap and the space 264 are the reverse complement of those shown for connecting the tap 204 with the space 266.

The motor speed controller The device for controlling the speed of the motor according to demand is illustrated in Figs. 11 and l2. It is indicated generally by the numeral 30E) and comprises a base 3$l2lto which are secured l twelve contact-carrying blades 304. More or less could of course be used. The blades are secured in conventional stacked relationship between insulating spacing blocks 385 so that their extreme ends project beyond the block in one direction and form terminals 328 while their opposite ends extend sufficiently in the opposite direction toA provide considerable flexibility. The ends of the blades are cut so that beginning at the top as shown, each blade is slightly longer Ythan the next adjacent blade located thereabove. The blades are biased so that they tend to spring upwardly beyond the central point somewhat v and are held downwardly by a tapered block 3 iii secured to the base by a screw 3l2. Each of the blades is provided with a contact adjacent its free end adapted to complete a circuit between the blade upon which it is secured and the next adjacent blade aboveand below when the blades are moved toward each other. Normally, however, when the free ends of all of the blades are against the block 3|8, the contacts will be separated.

The uppermost contact strip is formed at its free end to provide an eye 3 E 4 connected by means of a U-shaped link 3 I6 to a bimetal thermostatic blade 3| 8. The opposite end of this blade is secured to a block 328 journaled upon a pin 322. The opposite face of this block in turn is connected to a second bimetal element 324 which ex tends parallel to the thermostatic element 3i8. This strip 324 at its opposite end is secured to a yolk 326 which embraces an eccentric pin 328 which may be rotated relative to the base 332. Thus, by turning the eccentric pin 328, the leithand end of the thermostatic blade 324, as seen 'in Fig. 11, can be moved upwardly and downvthe bmetalv strip 3|8 will be raised somewhat.

This causes the free end of the bimetal strip to deiiect downwardly toward the dotted line posi- 15 tion shown in Fig. liso .as to urge the uppermost Contact` strip 3,84 downwardly. Upon .Slight downward movement, this contact is brought into engagement with the next' lower ,contact so as to complete a circuit lbetween the two top- Imost strips. Additional downward movement will urge the second strip into engagement with the third so as to short the three uppermost strips and so on. The top bimetal stripI 324 acts as an ambient temperature compensating ele mentso that changes in the `tempereture of the compartment wher-e the device is located will not a-EEect the operation of the motor controller. Normally, increasing the temperature in the space where the device is located would. have the same elect upon the bimetal strip 318 as would increasing the rate of current supply to vthe terminals 332. This is compensated for, however, be-

cause any ambient conditions whichcanse the lower bimetal strip 3|8 to flex so as to move its free end downwardly will also cause the upper strip 324 to ex similarly, thereby rotating the block 328 in such direction as to compensate for the downward movement of the free end ofV the lower element, The converse is of course also true. Thusjchanges in ambient temperature do not cause movement of the free end of the lower bimetal element.

The sending unit for supplying current to the heater 330 is shown diagrammatically in Fig. 22 whererit 'is indicated by the numeral 334. This device comprises a base 335 to which two opposed contacting bimetal elements 333 and 348 are attached. One of these elements, 333, is provided with a heater 342 connected at one end to the strip 338. The second of the strips 348 is controlled by an adjustment knob 344 threaded through a bracket 346 so that when the knob is turned in one direction the lower end thereof will press the strip 345 downwardly. When a device of this character is connected in series with the bimetal heater 338 such that current flows through the Vstrip 343, through the contacts to the strip 33B, thence to the heater .342 and nally through the power source and back to the heater 333, the flow of current will cause the tempera ture of the heater 342 to increase. This in turn heats the biinetal element 333 and causes its free end to move downwardly, thereby separating the contacts. As soon as this hap-pens, current ceases to flow, whereupon heater 342 and strip 338 Acool until the contacts are brought together once more. This cycle repeats itself endlessly and the length o the on and '01T periods willA dep-end upon the position of the contact secured to he strip 343. If this contact is in a higher location, less current will need to low through the heater .342 in order to separate the contacts, thereby giving longer oi -cycles and shorter on cycles. Theconverse is also true. Inasmuch as the strip 34 is a bimetal element sensitive -to the temperature of the sp-ace to be heated, t-he location ci the ccntactsecured thereto will be determined by the temperature of Vthe room. The direction V`of deflection of bimetal element ,-348 is such `that a decrease in tempera-ture tends to cause this element tofmove downwardly so as to send longer on cycles and shorter loff cycles. This causes the heater 338 to be energized for -a greater portion of time with the result that 'its Amean temperature rises. As vexplained previously, this causes the free Vend of this bimetal element to move vdownwardly, Aas seen in Fig. 11, .so as to shortsuccessive contacts mounted uponV the strip 3554, such that the greater the decrease in temperature Within the room,the more of these contacts will be sh'orted. A bank of resistance elements com prises a portion of this speed controller but has not been shown in detail since the connection would be more confusing than illuminating, it bein-g deemed sufficient to show these resistors diagrammatically in Fig. 22.

The .safety devices Among the control .devices provided in the heater .of the present invention which serve protective or safety functions or miscellaneous functions are a pair of relays which .may be of standard construction and therefore needno de scription, a lock-open type time-delay switch, an overheat switch, and a llame detector Which inluences the control circuit to be described presently approximately twenty seconds or sol vagiter combustion'hasfbeen established.

The flame detector is Villustrated in detail in Figs. 16 and 17 and comprises an jL-shaped bracket 348 having an opening 358 through which a small stainless steel tube 352 extends. One end of this tube is provided with a collar 354 so as to limit outward Amovement of the tube, this collar being in face-to-face relationship with the back surface of bracket .348. AThe opposite end .of the tube 352 is spun inwardly, 5as at 355, vso as to prevent outward movement of a short stai-nless steel plug 358 located `within the louter end of the tube. A loose-tting fused quartz rod 360 is located within the tube and supports a 'loosetting stainless steel plug 332 located near the opposite end of the tube. Plug 362 in turn supports a stem 354 urged against the plug 362 `-by a coiled spring 368. This coiled spring bears at one end against a keeper 368 attached -to the stem 364 While its opposite end presses against a portion of a bracket 318 welded to the L-shaped bracket 348. The bracket 310 is 'bent and drilled so as to form two spaced openings 3'12and 314 through Vwhich the stem 364 extends. These openings prevent lateral movement of the stem but permit it to move inwardly and outwardly.

Near its outer end, the stem 354 is provided with threads 31B which are fitted to a threaded collar 318 having an actuating finger 388 which extends through a slot 382 in the bracket 318 and serves to operate a snap-type electric switch 384. The extreme outer end of the stem 364 has a screw driver slot 386 for adjusting the position* of the actuation iinger 380 so as to determine the temperature at which the switch operates.

The switch 384 preferably is of the over-center snap type and may be of standard construction. Although the particular switch shown is manufactored by the Acro Electric Company of 1314 Superior Avenue, Cleveland, Ohio, and is known as Acro switch model M, it will be appreciated that there are numerous other types of small snap switches which would'be suitable for the purpose. The switch has contacts of lthe normally open type and completes the circuit between a :pair of leads 388 vand 390 when the finger 388 has been moved downwardly to a predetermined position.

'I'he flame detector is indicated lgenerally iby the 'numeral 392 and maybe seen in the assembled heater in Figs. 1I 2 and 4. It is mounted -upon the downstream end of the heatexchanger in suchvmanner that the stainless steel tube 352 Y projects into the 'hot gas `passage of Pthe heat manner. Whenever :the temperature in 'the ahot 

